The human spine normally has contours in the sagital (vertical) plane. A deformed spine may have contours in the coronal (horizontal) plane and/or the axial (rotational) plane. It has become a common surgical practice to insert one or two rods in the spine to straighten a deformed spine. Bone screws are placed in the pedacles of the backbone to secure the rods. The rods are pre-bent to the approximate corrective angles as taught by U.S. Pat. No. 5,113,685 (1992) to Asher et al. The rods are then inserted into the backbone and secured with clamps to the bone screws.
At this stage in the surgical procedure there needs to be made in situ adjustment bends to the rod(s). Space to access the rod(s) is at a premium. The clamps are usually spaced about four inches apart. The lamina (ridges) of the backbone complicate access to the rod(s). The rod(s) are full of blood and are slippery.
The rods are usually 1/4 inch in diameter and constructed of stainless steel. In situ bending also requires moving the rib cage and large portions of body mass. It takes all the strength of a surgeon to bend the rods even with the use of fifteen inch bending tools. If the bending tools slip off the rod during the in situ bending procedure, then injury to the patient can occur.
Known in the art is the Isola.RTM. In Situ Bender Model 2060-30 manufactured by Acromed. FIG. 1 shows the right hand Model 2060-30 bender 1. It is a stainless steel instrument having a tubular handle 2. A portion of the handle 2 has knurls 3. The working ends 4,6 are offset an angle .theta..sub.1 of about 10.degree.. Working end 4 has rod slot 5. W.sub.2 is 1/4 inch to accommodate a 1/4 inch stainless steel rod. A rod slot (not shown) on working end 6 has a width of 3/16 inch for a 3/16 inch rod. Each rod slot has a single central bore (B--B for rod slot 5).
In operation to grasp a rod (not shown) the rod slot 5 is placed on the rod, and a left bender (not shown) is placed at a desired point on the same rod. The surgeon then pushes or pulls the benders to obtain the desired bend.
There are no means to secure,the rod inside the rod slot 5 during the bending procedure. Thus, the rod is prone to slip out of the rod slot 5 during the bending procedure. This can injure a patient.
The present invention adds two additional bores besides the central axis bore B--B. Each additional bore is at about a 3.degree. angle off axis to B--B. This creates a keyhole notch which helps secure the rod during the bending operation. Additionally a new flat handle is provided rather than a tubular handle. This flat handle helps the surgeon to overcome rotational forces on the handle. The angle .theta..sub.1 of about 10.degree. is also increased to about 20.degree.. This permits a criss-crossing of the benders. The surgeon now has the option of squeezing or pushing the benders together rather than pulling them apart.
The dimensions of the prior art shown in FIG. 1 are as follows:
.theta..sub.1 =10.degree. PA1 W.sub.2 =1/4" PA1 W.sub.1 =7/16" PA1 d.sub.1 =131/2" PA1 d.sub.2 =3/4"